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The Three Mile Island nuclear plant was automatically shutdown Thursday after a coolant pump stopped working. The plant is the site of the United States' worst nuclear accident in 1979. NBC10's Claudia Rivero talked to Exelon officials and residents who live near the plant in Dauphin County, PA. (Published Friday, Sept. 21, 2012)

Editor's Note: This article was published on September 20, 2012.

One of the reactors at Three Mile Island automatically shut down Thursday afternoon after one of the reactor cooler pumps tripped, according to the Nuclear Regulatory Commission.

TMI has a computerized protection system that automatically shuts down the plant at any sign of possible trouble, according to the NRC. At 2:16 p.m, when the pump stopped operating, that triggered the shutdown.

"The automatic shutdown procedure is the first in a long line of safe cards in place," Stephen Libhart, Directof of Dauphin County Emergency Management, told NBC10.

An NRC inspector, who was already on site, went to the plant's control room to oversee the response, according to the NRC.

The reactor that shut down was Unit One, which also shut down automatically in August while it was being manually taken down for repairs.

People in the area, which is just outside of Harrisburg, Pa., reported hearing a loud noise during the shutdown. Officials say that was caused by the steam that gets released during a shutdown.

Libhart said the "monitoring equipment did not detect any release of harmful or otherwise radiation that would have impacted the area. There is no risk to the area, animals or individuals," he said. "No danger at all."

Plant workers are waiting now for the reactor to cool down enough so that they can go in and troubleshoot the pump problem.

"They will take a look at every system that they have to see what actually triggered the shutdown to make sure there's nothing to be addressed in terms of maintenance, repair or otherwise. I believe it takes a few days to go through a complete cool down process and do a restart," Libhart said.

We have a crew headed to Three Mile Island. Stay with NBC10 for the latest developments on this story.